Microprocessors Interview Questions o part ---14

Microprocessors Interview Questions of part ---14
What happens when HLT instruction is executed in processor?
The Micro Processor
enters into Halt-State and the buses are tri-stated.
What is Tri-state logic?
Three Logic Levels are used and they are High, Low, High impedance state. The high and low are normal logic levels & high impedance state is electrical open circuit conditions. Tri-state logic has a third line called enable line.
In 8085 which is called as High order / Low order Register?
Flag is called as Low order register & Accumulator is called as High order Register.
Why crystal is a preferred clock source?
Because of high stability, large Q (Quality Factor) & the frequency that doesn’t drift with aging. Crystal is used as a clock source most of the times.
What are the flags in 8086?
In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Interrupt flag, Direction flag, and Sign flag.
What is a Microprocessor?
Microprocessor is a program-controlled device, which fetches the instructions from memory, decodes and executes the instructions. Most Micro Processor
are single- chip devices.
How do you submit a form using JavaScript?
Use document.forms[0].submit()(0 refers to the index of the form – if we have more than one form in a page, then the first one has the index 0, second has index 1 and so on).
Write about the following instruction :
Offset of the first instruction of procedure is in two memory addresses in DS. It replaces the contents of IP with contents of word memory locations in DS pointed to by BX.
Write about EVEN directive in 8086 ALP.
It forces the address of the next byte to be even. 8086 words can be accessed in less time if they begin at even address.
While handling the interrupt instructions in 8086, What are the internal operations may be carried out by the stack?
(i)SP =SP-2 , stack ß Push flag reg. Contents, IF =0 , TF =0
(ii) SP=SP-2, Stackß CS Reg. Contents, Address of Interrupt pointer = Interrupt type * 4 , CS Register Contents ß Second word of Interrupt pointer
(iii) SP=SP-2, Stackß IP, IPß First word of Interrupt pointer
Define LAHF and SAHF instructions in 8086.
LAHF : Load the 8085 equivalent flags into the AH register.SAHF: Store the AH register into the low order byte of the flag register.
What is the use of TEST instruction in 8086?
Test instruction is the same as the AND instruction except that ite does not put the result anywhere. Like the CMP instruction , it is used only to set the flags.
What is Emulator?
Emulator
is a mixture of hardware and software .It is used to test and debug the hardware and software of an external system such as the prototype of a microprocessor based instrument.
Define EXTRN directive in in 8086 assembly language?
The EXTRN directive is used to inform the assembler that the names or labels following the directive are in some other assembly module.
Write the use of Assume directive in 8086 assembly language using one example?
Assume CS: code_here, DS:data_hereIt tells the assembler that the logical segment code_here contains the instruction statements for the program and should be treated as a code segment. It also tells the assembler that it should treat the logical segment data_here as the data segment for this program.